Current responsive device



Dec. 22, 1942. H. F. GRAVE ETAL CURRENT RESPONSIVE DEVICE Filed May 26,1941 Fig.8.

W E m c o r t we. g 3 M s m /Me Patented Dec. 22, 1942 CURRENTRESPONSIVE DEVICE Hans F. Grave, Berlin-Treptow,

Lingg, Berlin-Neukolln,

General Electric Comp New York and Gustav Germany, assignors to any, acorporation of Application May 26, 1941, Serial No. 395,314 In GermanyMay 30, 1940 2 Claims. Our invention relates to current-responsivedevices and concerns particularly such devices of the iron coredynamometer type.

It is an object of our invention to provide an improved construction andarrangement of the field windings and core of current responsive devicessuitable for use in dynamometer type instruments such as wattmeters andalternating current ammeters, voltmeters, relays, recorders, and thelike.

It is an object of our invention to provide a current-responsive devicewhich has high current capacity, high sensitivity, and high electricalefilciency with a reliable and durable mechanical construction.

Other and further objects will become apparent as the descriptionproceeds.

A better understanding of the invention will be afiorded by thefollowing detailed description considered in connection with theaccompanying drawing, and those features of the inven-- tion which arebelieved to be novel and patentable will be pointed out in the claimsappended hereto.

In the drawing Fig. 1 is a perspective view of the field structure of adynamometer type instrument having a field core composed of magnetizablematerial; Fig. 2 is a schematic diagram representing a plan view of thearrangement of Fig. 1 showing the flux lines of the magnetic field; Fig.3 is a perspective view of a modification of the arrangement of Figs. 1and 2; Fig. 4 is a schematic diagram representing a plan view 01' thearrangement of Fig. 3 showing the flux lines of the magnetic field; Fig.5 is a perspective view of an improvement in the arrangement of Figs. 1to 4, and Fig. 6 is a schematic diagram representing a plan view of theconstruction of Fig. 5 showing the direction of the lines of flux of themagnetic field. Like reference characters are utilized throughout thedrawing to designate like parts.

In accordance with our invention a field winding or stator winding isprovided with a magnetic circuit consisting of high-permeabilitymagnetizable material, such as soft iron for example. An annular spaceis provided in the magnetic material in which a movable coil may berotatably mounted. In the arrangement of Figs. 1 and 2 there is an outercore II having a circular opening surrounding an inner core I2 which iscylindrical in shape and sufficiently smaller in diameter than theopening in the outer core II to leave an annular air gap I3 tor amovable coil. A pair of diametrically opposed slots I4 and I5 isprovided in the outer core II to receive a field or stator winding whichmay be in the form of two coils I6 and I! having diametrically oppositecoil sides fitting in the slots I4 and I5. The coils I6 and I! mayoriginally be wound in circular form and inserted in the slots I4 and I5of the outer core I I before assembly with the inner core I2, whereuponthe coils I6 and Il may be bent over into the shape shown to permitinsertion of the center core I2 and to leave space for the rotatablecoil with any pointer or other mechanism which may be associated with arotatable coil.

When current is passed through the field coils I6 and I1 magnetic fiuxis caused to circulate in the magnetic core members II and I2 in twocircular groups of flux lines I8 and I9 which circulate around the coilsides which occupy the core slots I4 and I5 as illustrated in Fig. 2.These flux lines cross the annular air gap I3 to produce a suitable fluxpattern for causing deflection of a rotatable current-conducting coilwhich may be rotatably mounted in the air gap I3.

The danger of causing any damage to the insulation of the field coils I6and I! by reason of the assembly operation which involves bending themafter insertion in the core slots I4 and I5 may be obviated by windingthe field coil on a center core I2, as illustrated in Figs. 3 and 4. Inthis case diametrically opposite slots I4 and I5 are provided in thecenter core I2 to permit winding a single field coil 20 on the core I2without filling in part of the air gap I3. This arrangement, however,would necessitate the use of a rotatable coil which would be longer inthe direction of its axis of rotation unless the center core I2 wereprovided with grooves also in the top and bottom to permit fitting thetop and bottom of the field coil 20 into such grooves. This mightbeobjectionable, however, in the case of alternating current instrumentssince the cores I I and I2 would preferably be composed of laminatedpieces or thin plates in order to avoid excessive eddy current losses.

In order to avoid a reduction in cross-section of the magnetic path inthe center core produced by the slots I4 and I5, in order to avoid thepossibility of excessive heating which might result from the use of finewire to obtain the requisite number of turns of the coil 20 in the slotsI4 and I5 and, at the same time, to permit the use of a rotatable coilof minimum axial length, we may utilize the construction of Figs. 5 and6. In this case the stator core II is provided with diametricallyopposite stator-coil-re-' ceiving slots l4 and I5 and the stator windingconsists of two coils 2| and 22 having coil sides occupying the coreslots l4 and I5 respectively. The coils 2| and 22, however, are woundaround the diametrically opposite sides 23 and 24 of the stator core II,which may be roughly elliptical in shape, in order to provide adequatecore crosssection in spite of the presence of the slots H and I5. Ifdesired, the outer stator core I I may be composed of symmetricallaminations each forming half of an elliptical figure so that the statorcore is divided into two parts by the major axis of the ellipse alongdividing lines 25 and 26 (Fig. 6) within the stator coils 2| and 22.This permits the use of preformed stator coils, if desired, and resultsin substantially no stray or leakage flux since the magnetic joints 25and 28 are within the stator coils 2| and 22. The effect of the joints25 and 26 on the magnetic reluctance is negligible in comparison withthe air gap l3.

It will be understood that for use with an annular air gap IS a movablecoil 21 may be employed having an axis of rotation substantiallycoincident with the center axis of the cylindrical center core l2 andhaving supporting pivots or a shaft 3| lying along the axis of rotationand carrying a pointer 32. Any suitable mounting means for the rotatablecoil 21 and the center core |2 may be employed.

In the arrangement of Figs. 5 and 6, the center core l2 may be rotatablewith the coil 21 or may be secured to a stationary part of the apparatusin any well-known manner. In the lattercase, since the maximum fieldintensity occurs in the portions 28 and 25 of the air gap l3. theseportions of the air gap will preferably be left free for movement of therotatable coil 21; e. g. the inner core |2 may be secured to the outercore II by means of a pair of brass-strip angle brackets 30 screwed tothe cores H and I2.

We have herein shown and partially described certain embodiments of ourinvention and certain methods of operation embraced therein for thepurpose of explaining its practice and showing its application, but itwill be obvious to those skilled in the art that many modifications andvariations are possible, and we aim therefore to cover ll suchmodifications and variations as fall within the scope of our inventionwhich are defined in the appended claims.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A dynamometer type current-measuring instrument comprising a roughlyelliptical outer core having a substantially circular opening therein, astationary center core having a substantially circular outer surface, afield winding and a rotatable winding, the center core being locatedwithin the outer core and spaced therefrom around the entire peripheryof the center core to leave a substantially annular air gap around theperiphery sufllcient for the rotatable winding, said rotatable windingbeing rotatably mounted on an axis of rotation substantially coincidentwith the axis of the annular air gap and surrounding said center core,said outer core having a pair of relatively short slots out thereinextending radially outward from the circular opening therein and alongthe major axis of the elliptical outer core and said field windingconsisting of current-conducting coil means having coil sides occupyingsaid core slots.

2. A dynamometer type current-measuring instrument comprising a roughlyelliptical outer core having a substantially circular opening thereinand divided along the major elliptical axis, a stationary center corehaving a substantially circular outer surface, a field winding and arotatable winding, the center core being located within the outer coreand spaced therefrom to leave a substantially annular air gap sufficientfor the rotatable winding, said rotatable winding surrounding saidcenter core and being rotatably mounted on an axis of rotationsubstantially coincident with the axis of the annular air gap, saidouter core having a pair of relatively short slots cut therein extendingradially outward from the circular opening in the outer core along thesaid major elliptical axis so as to be divided thereby, and said fieldwinding consisting of preformed current-conducting coil means havingcoil sides occupying said core slots and linking said outer core aroundthe lines of division therein whereby the portion of maximum reluctanceof the outer core falls within the coil means and the leakage flux isminimized.

HANS F. GRAVE. GUSTAV LINGG.

